Distance measurement device, distance measurement method, and distance measurement program

ABSTRACT

A distance measurement device includes an imaging unit which captures a subject image formed by an imaging optical system forming the subject image indicating a subject, an emission unit which emits directional light as light having directivity along an optical axis direction of the imaging optical system, a light receiving unit which receives reflected light of directional light from the subject, a derivation unit which derives a distance to the subject based on a timing at which directional light is emitted by the emission unit and a timing at which reflected light is received by the light receiving unit, and a control unit which performs control such that at least a part of an imaging period by the imaging unit overlaps at least a part of a distance measurement period by the emission unit, the light receiving unit, and the derivation unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of, and claims priorityto, U.S. patent application Ser. No. 16/817,897, filed Mar. 13, 2020,which is a continuation application of, and claims priority to, U.S.patent application Ser. No. 15/333,146, filed Oct. 24, 2016, which is acontinuation application of International Application No.PCT/JP2015/056876, filed Mar. 9, 2015. Further, this application claimspriority from Japanese Patent Application No. 2014-095557, filed May 2,2014, and Japanese Patent Application No. 2014-159803, filed Aug. 5,2014. The disclosures of all the applications listed above areincorporated herein by reference in their entireties.

BACKGROUND 1. Technical Field

A technique of the present disclosure relates to a distance measurementdevice, a distance measurement method, and a distance measurementprogram.

2. Related Art

JP2008-96181A discloses a device including time detection means fordetecting the time from the emission of measurement light to thereception of measurement light by light receiving means, shake amountdetection means for detecting a shake amount of a housing duringemission of measurement light when measurement light is emitted fromlight emitting means, and distance determination means for determiningthe distance to an object to be measured based on the time detected bythe time detection means and the shake amount detected by the shakeamount detection means.

JP2002-207163A discloses a distance measurement and imaging devicehaving a distance measurement function of measuring a distance to asubject by irradiating the subject with a laser beam along an opticalaxis of a lens and detecting reflected light of the laser beam and animaging function of imaging the subject.

SUMMARY

However, in the above-described distance measurement and imaging device,since imaging is performed regardless of the distance measurement, it isdifficult to efficiently perform imaging and the distance measurement.

An embodiment of the invention has been suggested in consideration ofsuch a situation, and provides a distance measurement device, a distancemeasurement method, and a distance measurement program capable ofefficiently executing imaging and a distance measurement.

In order to attain the above-described object, a distance measurementdevice according to a first aspect of the invention comprises an imagingoptical system which forms a subject image indicating a subject, animaging unit which captures the subject image formed by the imagingoptical system, an emission unit which emits directional light as lighthaving directivity along an optical axis direction of the imagingoptical system, a light receiving unit which receives reflected light ofthe directional light from the subject, a derivation unit which derivesa distance to the subject based on a timing at which the directionallight is emitted by the emission unit and a timing at which thereflected light is received by the light receiving unit, and a controlunit which performs control such that at least a part of an imagingperiod by the imaging unit overlaps at least a part of a distancemeasurement period by the emission unit, the light receiving unit, andthe derivation unit. With this, the distance measurement deviceaccording to the first aspect of the invention can efficiently executeimaging and a distance measurement compared to a case where an imagingperiod and a distance measurement period do not overlap each other.

According to a second aspect of the invention, in the distancemeasurement device according to the first aspect of the invention, thecontrol unit may perform control such that the imaging start timing bythe imaging unit and the distance measurement start timing by theemission unit, the light receiving unit, and the derivation unit aresynchronized with each other. With this, the distance measurement deviceaccording to the second aspect of the invention can efficiently executeimaging and a distance measurement compared to a case where a distancemeasurement is started at a timing later than a timing at which imagingis started.

According to a third aspect of the invention, in the distancemeasurement device according to the second aspect of the invention, theimaging start timing may be a timing at which actual exposure by theimaging unit is started. With this, the distance measurement deviceaccording to the third aspect of the invention can efficiently executeimaging and a distance measurement compared to a case where a distancemeasurement is started at a timing later than the timing at which actualexposure is started.

According to a fourth aspect of the invention, in the distancemeasurement device according to the first aspect of the invention, thecontrol unit may perform control such that the timing at which theactual exposure by the imaging unit ends and the distance measurementstart timing by the derivation unit are synchronized with each other.With this, the distance measurement device according to the fourthaspect of the invention can efficiently execute imaging and a distancemeasurement compared to a case where a distance measurement is startedat a timing later than a timing at which actual exposure ends.

According to a fifth aspect of the invention, in the distancemeasurement device according to the first aspect of the invention, thecontrol unit may perform control such that the reading end timing ofsignal charges according to the actual exposure by the imaging unit andthe distance measurement start timing by the emission unit, the lightreceiving unit, and the derivation unit are synchronized with eachother. The distance measurement device according to the fifth aspect ofthe invention can efficiently execute imaging and a distance measurementcompared to a case where a distance measurement is started at the timinglater than the reading end timing of the signal charges.

According to a sixth aspect of the invention, in the distancemeasurement device according to any one of the first to fifth aspects ofthe invention, the derivation unit may perform the derivation of thedistance multiple times and may derive a distance having a highfrequency among the distances obtained by deriving the distance multipletimes as a final distance. With this, the distance measurement deviceaccording to the sixth aspect of the invention can derive a distancehighly necessary for the user as a final distance compared to a casewhere the distance having a high frequency among the distances obtainedby performing the derivation of the distance to the subject multipletimes is not output.

According to a seventh aspect of the invention, in the distancemeasurement device according to the sixth aspect of the invention, in acase of deriving the distance, the derivation unit may determine adistance range for use when determining the frequency or a time rangefrom the emission of the directional light to the reception of thedirectional light based on focusing state specification information andmay derive the final distance within the determined distance range orthe determined time range. With this, the distance measurement deviceaccording to the seventh aspect of the invention can derive a distancewithin a distance range focused by the user as a final distance comparedto a case where the distance to the subject is not derived based on adistance range or a time range determined based on an adjustment result.

According to an eighth aspect of the invention, in the distancemeasurement device according to the seventh aspect of the invention, ina case of deriving the distance, the derivation unit may derive thefinal distance with a resolution determined according to a result ofdetermination of the distance range or the time range. With this, thedistance measurement device according to the eighth aspect of theinvention can minutely derive a final distance compared to a case wherethe distance to the subject is derived without using the resolutiondetermined according to a result of determination of a distance range ora time range.

According to a ninth aspect of the invention, in the distancemeasurement device according to any one of the first to eighth aspectsof the invention, the emission unit may be able to adjust the emissionintensity of the directional light and may adjust the emission intensitybased on at least one of focusing state specification information orsubject brightness or exposure state specification information to emitthe directional light. With this, the distance measurement deviceaccording to the ninth aspect of the invention can suppress the emissionof directional light by the emission unit in a state where the emissionintensity is excessive and deficient compared to a case where theemission intensity of directional light is adjusted without using any offocusing state specification information, subject brightness, andexposure state specification information.

According to a tenth aspect of the invention, in the distancemeasurement device according to the ninth aspect of the invention, theemission unit may make the emission intensity lower when a focaldistance indicated by the focusing state specification information isshorter. With this, the distance measurement device according to thetenth aspect of the invention can suppress the emission of directionallight by the emission unit in a state where the emission intensity isexcessive and deficient compared to a case where a configuration inwhich the shorter the focal distance, the lower the emission intensityis not provided.

According to an eleventh aspect of the invention, in the distancemeasurement device according to the ninth or tenth aspect of theinvention, the emission unit may make the emission intensity lower whenthe subject brightness is lower and may make the emission intensitylower when the exposure indicated by the exposure state specificationinformation is higher. With this, the distance measurement deviceaccording to the eleventh aspect of the invention can suppress theemission of directional light by the emission unit in a state where theemission intensity is excessive and deficient compared to a case where aconfiguration in which the higher the exposure, the lower the emissionintensity is not provided.

According to a twelfth aspect of the invention, in the distancemeasurement device according to any one of the first to eleventh aspectsof the invention, the light receiving unit may be able to adjust lightreceiving sensitivity and may adjust the light receiving sensitivitybased on focusing state specification information to receive thereflected light. With this, the distance measurement device according tothe twelfth aspect of the invention can suppress the reception ofreflected light by the light receiving unit in a state where the lightreceiving sensitivity is excessive and deficient compared to a casewhere the light receiving sensitivity of the light receiving unit isadjusted without using focusing state specification information.

According to a thirteenth aspect of the invention, in the distancemeasurement device according to the twelfth aspect of the invention, thelight receiving unit may make the light receiving sensitivity lower whena focal distance indicated by the focusing state specificationinformation is shorter. With this, the distance measurement deviceaccording to the thirteenth aspect of the invention can suppress thereception of reflected light by the light receiving unit in a statewhere the light receiving sensitivity is excessive and deficientcompared to a case where a configuration in which the shorter the focaldistance obtained as a result of focus adjustment, the lower the lightreceiving sensitivity is not provided.

According to a fourteenth aspect of the invention, the distancemeasurement device according to any one of the first to thirteenthaspects of the invention may further comprise a display unit whichdisplays an image, and the control unit may perform control such thatthe display unit displays a motion image captured by the imaging unitand displays information relating to the distance to the subject derivedby the derivation unit. With this, the distance measurement deviceaccording to the fourteenth aspect of the invention can make the useraccurately ascertain the relationship between the state of the subjectand the distance to the subject compared to a case where informationrelating to the distance to the subject is not displayed in parallelwith the display of a motion image.

According to a fifteenth aspect of the invention, in the distancemeasurement device according to any one of the first to fourteenthaspects of the invention, a distance measurement by the emission unit,the light receiving unit, and the derivation unit may be performed anumber of times determined in advance according to subject brightness orexposure state specification information. With this, the distancemeasurement device according to the fifteenth aspect of the inventioncan obtain a distance measurement result, in which the influence ofnoise of ambient light is moderated, compared to a case where the lightemission frequency of directional light is fixed regardless of subjectbrightness.

According to a sixteenth aspect of the invention, in the distancemeasurement device according to the fifteenth aspect of the invention, adistance measurement by the emission unit, the light receiving unit, andthe derivation unit may be performed a larger number of times when thesubject brightness is higher or when the exposure indicated by theexposure state specification information is lower. With this, thedistance measurement device according to the sixteenth aspect of theinvention can obtain a distance measurement result, in which theinfluence of noise of ambient light is moderated, compared to a casewhere the light emission frequency of directional light is fixedregardless of high subject brightness.

According to a seventeenth aspect of the invention, the distancemeasurement device according to any one of the first to sixteenthaspects of the invention may further comprise a storage unit whichstores the distance derived by the derivation unit, and the storage bythe storage unit may be stopped in a case where the derivation of thedistance by the derivation unit is impossible. With this, the distancemeasurement device according to the seventeenth aspect of the inventioncan prevent storage of incomplete distance data.

According to an eighteenth aspect of the invention, the distancemeasurement device according to the seventeenth aspect of the inventionmay further comprise a storage setting unit which sets whether or not tostop storage by the storage unit in a case where the derivation of thedistance by the derivation unit is impossible. With this, the distancemeasurement device according to the eighteenth aspect of the inventioncan set whether or not to perform storage into the storage unitaccording to a user's intention in a case where the derivation of thedistance is impossible.

According to a nineteenth aspect of the invention, in the distancemeasurement device according to any one of the first to eighteenthaspects of the invention, the derivation unit may derive the distance ina case where there is no focus adjustment error by a focus adjustmentunit performing focus adjustment of the imaging optical system withrespect to the subject and there is no exposure adjustment error by anexposure adjustment unit adjusting exposure in a case where the imagingunit performs imaging. With this, the distance measurement deviceaccording to the nineteenth aspect of the invention can obtain adistance measurement result along with an image subjected to focusingand exposure adjustment.

In order to attain the above-described object, a distance measurementmethod according to a twentieth aspect of the invention comprisesderiving a distance to a subject based on a timing at which directionallight is emitted by an emission unit emitting directional light as lighthaving directivity along an optical axis direction of an imaging opticalsystem forming a subject image indicating the subject and a timing atwhich reflected light is received by a light receiving unit receivingthe reflected light of the directional light from the subject, andperforming control such that at least a part of an imaging period by animaging unit capturing a subject image formed by the imaging opticalsystem overlaps at least a part of a distance measurement period. Withthis, the distance measurement method according to the twentieth aspectof the invention can efficiently execute imaging and a distancemeasurement compared to a case where an imaging period and a distancemeasurement period do not overlap each other.

In order to attain the above-described object, a distance measurementprogram according to a twenty-first aspect of the invention causes acomputer to execute processing comprising deriving a distance to asubject based on a timing at which directional light is emitted by anemission unit emitting directional light as light having directivityalong an optical axis direction of an imaging optical system forming asubject image indicating the subject and a timing at which reflectedlight is received by a light receiving unit receiving the reflectedlight of the directional light from the subject, and performing controlsuch that at least a part of an imaging period by an imaging unitcapturing a subject image formed by the imaging optical system overlapsat least a part of a distance measurement period. With this, thedistance measurement program according to the twenty-first aspect of theinvention can efficiently execute imaging and a distance measurementcompared to a case where an imaging period and a distance measurementperiod do not overlap each other.

According to an embodiment of the invention, it is possible toefficiently execute imaging and a distance measurement compared to acase where an imaging period and a distance measurement period do notoverlap each other.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments according to the technique of the presentdisclosure will be described in detail based on the following figures,wherein:

FIG. 1 is a block diagram showing an example of the configuration of amain part of a distance measurement device according to an embodiment;

FIG. 2 is a timing chart showing an example of a timing of a distancemeasurement operation to measure a distance to a subject in the distancemeasurement device according to the embodiment;

FIG. 3 is a timing chart showing an example of a timing from lightemission to light reception in a single measurement in the distancemeasurement device of the embodiment;

FIG. 4 is a graph showing an example of a histogram of measured valuesin a case where a distance to a subject is set as a horizontal axis anda measurement frequency is set as a vertical axis;

FIG. 5 is a flowchart showing an example of a flow of control processingwhich is executed by a main control unit of the distance measurementdevice according to the embodiment;

FIG. 6A is a flowchart showing an example of a flow of distancemeasurement processing which is executed by a distance measurementcontrol unit of the distance measurement device according to theembodiment;

FIG. 6B is a continuation of the flowchart shown in FIG. 6A;

FIG. 7 is an example of a timing chart showing the timings of an imagingoperation and a distance measurement operation in the distancemeasurement device according to the embodiment;

FIG. 8 is an example of a timing chart showing a modification example ofthe timings of an imaging operation and a distance measurement operationin the distance measurement device according to the embodiment;

FIG. 9A is a modification example of a histogram obtained in thedistance measurement device according to the embodiment, and is adiagram illustrating an example of deriving a distance to a subjectwithout using a measurement result other than a subject distance rangebased on AF;

FIG. 9B is a modification example of a histogram obtained in thedistance measurement device according to the embodiment, and is adiagram illustrating an example of deriving a distance to a subjectwithout using a measured value of a distance less than a subjectdistance based on AF;

FIG. 9C is a modification example of a histogram obtained in thedistance measurement device according to the embodiment, and is adiagram illustrating an example of deriving a distance to a subjectwithout using a measured value of a distance longer than a subjectdistance based on AF;

FIG. 10 is a block diagram showing an example of adjustment of a drivevoltage based on AF and AE results;

FIG. 11 is a conceptual diagram showing an example of the configurationof a light emission frequency determination table;

FIG. 12 is a flowchart showing an example of a flow of brightnessinformation transmission processing; and

FIG. 13 is a flowchart showing an example of a flow of light emissionfrequency determination processing.

FIG. 14 is a conceptual diagram showing another example of theconfiguration of a light emission frequency determination table.

FIG. 15 is a flowchart showing another example of a flow of exposurestate specification information transmission processing.

FIG. 16 is a flowchart showing another example of a flow of lightemission frequency determination processing.

DETAILED DESCRIPTION

Hereinafter, an example of an embodiment of a distance measurementdevice according to the technique of the present disclosure will bedescribed referring to the accompanying drawings. In this embodiment, a“distance measurement” indicates a measurement of a distance to asubject to be a measurement target. In this embodiment, the magnitude ofexposure has the same meaning as the level of exposure.

First, the configuration of the distance measurement device according tothis embodiment will be described. FIG. 1 is a block diagram showing theconfiguration of a main part of a distance measurement device 10according to this embodiment.

The distance measurement device 10 of this embodiment has a function ofperforming a distance measurement and a function of imaging a subject togenerate a captured image indicating the subject. The distancemeasurement device 10 of this embodiment comprises a control unit 20, alight emitting lens 30, a laser diode 32, a light receiving lens 34, aphotodiode 36, an imaging optical system 40, an imaging element 42, anoperating unit 44, a view finder 46, and a storage unit 48.

The control unit 20 comprises a time counter 22, a distance measurementcontrol unit 24, and a main control unit 26. The time counter 22 has afunction of generating a count signal in each given period determined inadvance according to a signal (for example, a clock pulse) input fromthe main control unit 26 through the distance measurement control unit24.

The distance measurement control unit 24 has a function of performing adistance measurement under the control of the main control unit 26. Thedistance measurement control unit 24 of this embodiment controls thedriving of the laser diode 32 at a timing according to the count signalgenerated by the time counter 22 to perform the distance measurement.The distance measurement control unit 24 functions as a derivation unitaccording to the technique of the present disclosure. Specific examplesof the distance measurement control unit 24 include an applicationspecific integrated circuit (ASIC), a field-programmable gate array(FPGA), and the like. The distance measurement control unit 24 of thisembodiment has a storage unit (not shown). Specific examples of thestorage unit in the distance measurement control unit 24 include anonvolatile storage unit, such as a read only memory (ROM), and avolatile storage unit, such as a random access memory (RAM).

The main control unit 26 has a function of controlling the entiredistance measurement device 10. The main control unit 26 of thisembodiment has a function of controlling the imaging optical system 40and the imaging element 42 to image a subject and generating a capturedimage (subject image). The main control unit 26 functions as a controlunit, a brightness detection unit, a focus adjustment unit, and anexposure adjustment unit according to the technique of the presentdisclosure. Specific examples of the main control unit 26 include acentral processing unit (CPU) and the like. The distance measurementcontrol unit 24 of this embodiment has a storage unit (not shown).Specific examples of the storage unit in the distance measurementcontrol unit 24 include a nonvolatile storage unit, such as a ROM, and avolatile storage unit, such as a RAM. A program of control processingdescribed below is stored in the ROM in advance.

A program of control processing is not necessarily stored in the maincontrol unit 26 from the beginning. For example, a control program maybe stored in advance in an arbitrary portable storage medium, such as asolid state drive (SSD), a CD-ROM, a DVD disk, a magneto-optical disk,or an IC card. The distance measurement device 10 may acquire thecontrol program from the portable storage medium storing the program andmay store the control program in the main control unit 26 or the like.Furthermore, the distance measurement device 10 may acquire the controlprogram from other external devices through the Internet or a local areanetwork (LAN) and may store the control program in the main control unit26 or the like.

The operating unit 44 is a user interface which is operated by the userwhen various instructions are provided to the distance measurementdevice 10. The operating unit 44 includes a release button, a distancemeasurement instruction button, and buttons, keys, or the like (all ofthese are not shown) which are used when the user provides variousinstructions. Various instructions received by the operating unit 44 areoutput to the main control unit 26 as operation signals, and the maincontrol unit 26 executes processing according to the operation signalsinput from the operating unit 44.

The release button of the operating unit 44 detects a two-stage pressingoperation of an imaging preparation instruction state and an imaginginstruction state. The imaging preparation instruction state indicates,for example, a state of being pressed from a standby position to anintermediate position (half-pressing position), and the imaginginstruction state indicates a state of being pressed to a final pressingposition (fully pressing position) beyond the intermediate position.Hereinafter, “the state of being pressed from the standby position tothe half-pressing position” refers to a “half-pressing state”, and “thestate of being pressed from the standby position or the half-pressingposition to the fully pressing position” refers to a “fully pressingstate”.

In the distance measurement device 10 according to this embodiment, amanual focus mode and an auto-focus mode are selectively set accordingto a user's instruction. In the auto-focus mode, adjustment of imagingconditions is performed by bringing the release button of the operatingunit 44 into the half-pressing state, and then, exposure (imaging) isperformed by successively bringing the release button into the fullypressing state. That is, if the release button of the operating unit 44is brought into the half-pressing state, an automatic exposure (AE)function is operated to perform exposure adjustment, and an auto-focus(AF) function is operated to perform focusing control, and if therelease button is brought into the fully pressing state, imaging isperformed.

The storage unit 48 primarily stores image data obtained by imaging, anda nonvolatile memory is used therefor. Specific examples of the storageunit 48 include a flash memory or a hard disk drive (HDD).

The view finder 46 has a function of displaying images, characterinformation, and the like. The view finder 46 of this embodiment is anelectronic view finder (hereinafter, referred to as “EVF”), and is usedfor displaying a live view image (through-image) as an example of acontinuous-frame image obtained by imaging in continuous frames duringimaging. The view finder 46 is also used for displaying a still image asan image of a single-frame image obtained by imaging in a single framein a case where an instruction to capture a still image is provided. Inaddition, the view finder 46 is also used for displaying a reproducedimage in a playback mode or displaying a menu screen or the like.

The imaging optical system 40 comprises an imaging lens including afocus lens, a motor, a slide mechanism, and a shutter (all of these arenot shown). The slide mechanism moves the focus lens along the opticalaxis direction (not shown) of the imaging optical system 40. The focuslens is attached so as to be slidable along the optical axis directionof the slide mechanism. The motor is connected to the slide mechanism,and the slide mechanism receives power of the motor and slides the focuslens along the optical axis direction. The motor is connected to themain control unit 26 of the control unit 20, and is controlled anddriven according to a command from the main control unit 26. In thedistance measurement device 10 of this embodiment, as a specific exampleof the motor, a stepping motor is applied. Accordingly, the motor isoperated in synchronization with pulse power in response to a commandfrom the main control unit 26.

In the distance measurement device 10 according to this embodiment, inthe auto-focus mode, the main control unit 26 performs focusing controlby driving and controlling the motor of the imaging optical system 40such that a contrast value of an image obtained by imaging with theimaging element 42 becomes the maximum. Furthermore, in the auto-focusmode, the main control unit 26 calculates AE information which is aphysical quantity indicating brightness of an image obtained by imaging.The main control unit 26 derives a shutter speed and an F-numberaccording to the brightness of the image indicated by the AE informationwhen the release button of the operating unit 44 is brought into thehalf-pressing state. The main control unit 26 performs exposureadjustment by controlling respective related units such that the derivedshutter speed and F-number (aperture value) are obtained.

The imaging element 42 is an imaging element comprising color filters(not shown), and functions as an imaging unit according to the techniqueof the present disclosure. In this embodiment, as an example of theimaging element 42, a CMOS type image sensor is used. The imagingelement 42 is not limited to a CMOS type image sensor, and may by, forexample, a CCD image sensor. The color filters include a G filtercorresponding green (G) most contributing to obtaining a brightnesssignal, an R filter corresponding to red (R), and a B filtercorresponding to blue (B). Any filter of “R”, “G”, and “B” included inthe color filters is allocated to each of the pixels (not shown) of theimaging element 42.

In a case of imaging a subject, image light indicating the subject isformed on the light receiving surface of the imaging element 42 throughthe imaging optical system 40. The imaging element 42 has a plurality ofpixels (not shown) arranged in a matrix in a horizontal direction and avertical direction, and signal charges according to image light arestored in the pixels of the imaging element 42. The signal chargesstored in the pixels of the imaging element 42 are sequentially read asdigital signals according to the signal charges (voltages) under thecontrol of the main control unit 26.

In the distance measurement device 10 according to this embodiment, thesignal charges are sequentially read in units of pixels for eachhorizontal direction, that is, for each pixel row. In a period from whenthe electric charges are read from the pixels of one pixel row until theelectric charges are read from the pixels of the next pixel row, aperiod (hereinafter, referred to as a “horizontal blanking period”)during which the signal charges are not read is generated.

The imaging element 42 has a so-called electronic shutter function, andoperates the electronic shutter function to control an electric chargestorage time (shutter speed) of each photosensor at a timing under thecontrol of the main control unit 26.

The imaging element 42 outputs the digital signals indicating the pixelvalues of the captured image from the respective pixels. The capturedimage output from the respective pixels is a chromatic image, and is,for example, a color image having the same color arrangement as thepixel arrangement. The captured image (frames) output from the imagingelement 42 is temporarily stored (overwritten and saved) in the storageunit of the main control unit 26 or a RAW image storage area (not shown)of the storage unit 48 determined in advance through the main controlunit 26.

The main control unit 26 subjects the frames to various kinds of imageprocessing. The main control unit 26 has a white balance (WB) gain unit,a gamma correction unit, and a synchronization processing unit (all ofthese are not shown), and sequentially performs signal processing forthe original digital signals (RAW images) temporarily stored in the maincontrol unit 26 or the like in each processing unit. That is, the WBgain unit executes white balance (WB) adjustment by adjusting the gainof each of R, G, and B signals. The gamma correction unit performs gammacorrection of each of the R, G, and B signals subjected to the WBadjustment in the WB gain unit. The synchronization processing unitperforms color interpolation processing corresponding to the arrangementof the color filters of the imaging element 42 and generates thesynchronized R, G, and B signals. Each time the RAW image for one screenis acquired by the imaging element 42, the main control unit 26 performsimage processing for the RAW image in parallel.

The main control unit 26 outputs image data of the generated capturedimage for recording to an encoder (not shown), which converts an inputsignal to a signal in a different format. The R, G, and B signalsprocessed by the main control unit 26 are converted (encoded) to signalsfor recording by the encoder, and the signals for recording are recordedin the storage unit 48. The captured image for display processed by themain control unit 26 is output to the view finder 46. Hereinafter, forconvenience of description, in a case where there is no need fordistinction between the “captured image for recording” and the “capturedimage for display”, the expression “for recording” and the expression“for display” are omitted and the captured image for recording and thecaptured image for display are referred to as “captured images”.

The main control unit 26 of this embodiment displays a live view imageon the view finder 46 by performing control for continuously displayingthe captured images for display as a motion image.

The light emitting lens 30 and the laser diode 32 function as an exampleof an emission unit according to the technique of the presentdisclosure. The laser diode 32 is driven based on an instruction fromthe distance measurement control unit 24 and has a function of emittinga laser beam toward the subject to be a measurement target through thelight emitting lens 30 in the optical axis direction of the imagingoptical system 40. Specific examples of the light emitting lens 30 ofthis embodiment include an objective lens or the like. The laser beamemitted from the laser diode 32 is an example of directional lightaccording to the technique of the present disclosure.

The light receiving lens 34 and the photodiode 36 function as an exampleof a light receiving unit according to the technique of the presentdisclosure. The photodiode 36 has a function of receiving the laser beamemitted from the laser diode 32 and reflected from the subject throughthe light receiving lens 34 and outputting an electrical signalaccording to the amount of received light to the distance measurementcontrol unit 24.

If the user provides an instruction to measure a distance using thedistance measurement instruction button or the like of the operatingunit 44, the main control unit 26 instructs the distance measurementcontrol unit 24 to perform a distance measurement. Specifically, in thisembodiment, the main control unit 26 instructs the distance measurementcontrol unit 24 to perform a distance measurement by transmitting adistance measurement instruction signal to the distance measurementcontrol unit 24. In a case of performing a measurement of a distance toa subject and imaging of the subject in parallel, the main control unit26 transmits a synchronization signal for synchronizing a distancemeasurement operation and an imaging operation to the distancemeasurement control unit 24.

If the synchronization signal and the distance measurement instructionsignal are received, the distance measurement control unit 24 controlsthe light emission of the laser diode 32 at the timing according to thecount signal of the time counter 22 and controls a timing of emitting alaser beam toward the subject. The distance measurement control unit 24samples the electric signal according to the amount of received lightoutput from the photodiode 36 at the timing according to the countsignal of the time counter 22.

The distance measurement control unit 24 derives the distance to thesubject based on the light emission timing at which the laser diode 32emits a laser beam and the light reception timing at which thephotodiode 36 receives the laser beam, and outputs distance datarepresenting the derived distance to the main control unit 26. The maincontrol unit 26 displays information relating to the distance to thesubject on the view finder 46 based on distance data. The main controlunit 26 stores distance data in the storage unit 48.

The measurement of the distance to the subject by the distancemeasurement control unit 24 will be described in more detail. FIG. 2 isa timing chart showing an example of a timing of the distancemeasurement operation in the measurement of the distance to the subjectin the distance measurement device 10.

In the distance measurement device 10 of this embodiment, a singledistance measurement (measurement) sequence includes a voltageadjustment period, an actual measurement period, and a pause period. Thevoltage adjustment period refers to a period during which a drivevoltage of the laser diode 32 and the photodiode 36 is adjusted to anappropriate voltage value. As a specific example, in the distancemeasurement device 10 of this embodiment, as shown in FIG. 2 , thevoltage adjustment period is set to several 100 msec (milliseconds).

The actual measurement period refers to a period in which the distanceto the subject is actually measured. In the distance measurement device10 of this embodiment, as a specific example, as shown in FIG. 2 , thedistance to the subject is measured by repeating an operation to emit alaser beam and to receive the laser beam reflected from the subjectseveral 100 times and measuring the elapsed time from light emission tolight reception. That is, in the distance measurement device 10 of thisembodiment, in the single measurement sequence, the measurement of thedistance to the subject is performed several 100 times.

FIG. 3 is an example of a timing chart showing the timing from lightemission to light reception in a single measurement. In a case ofperforming a distance measurement, the distance measurement control unit24 outputs a laser trigger for causing the laser diode 32 to emit lightaccording to the count signal of the time counter 22 to the laser diode32. The laser diode 32 emits light according to the laser trigger. Inthe distance measurement device 10 of this embodiment, as a specificexample, the light emission time of the laser diode 32 is set to several10 nsec (nanoseconds). The emitted laser beam is emitted toward thesubject through the light emitting lens 30 in the optical axis directionof the imaging optical system 40. The laser beam emitted from thedistance measurement device 10 is reflected from the subject and reachesthe distance measurement device 10. The photodiode 36 of the distancemeasurement device 10 receives the reflected laser beam through thelight receiving lens 34.

In the distance measurement device 10 of this embodiment, as a specificexample, the distance measurement device performs a distance measurementfor a subject within several km from the distance measurement device 10.The time until the laser beam emitted from the laser diode 32 toward thesubject several km ahead through the light emitting lens 30 is returned(received) becomes several km×2/light speed=severalμsec (microseconds).Accordingly, in order to measure the distance to the subject several kmahead, as an example, as shown in FIG. 2 , the time of at least severalμsec is required.

In the distance measurement device 10 of this embodiment, thereciprocation time or the like of the laser beam is considered, and as aspecific example, a single measurement time is set to several msec asshown in FIG. 2 . Since the reciprocation time of the laser beam isdifferent depending on the distance to the subject, the measurement timefor each time may be different depending on the distance assumed by thedistance measurement device 10.

In the distance measurement device 10, the distance measurement controlunit 24 derives the distance to the subject based on measured valuesobtained by performing a measurement several 100 times as describedabove. In the distance measurement control unit 24 of this embodiment,as a specific example, a histogram of measured values for several 100times is analyzed to derive the distance to the subject. FIG. 4 is agraph showing an example of a histogram of measured values in a casewhere the distance to the subject is set as a horizontal axis and themeasurement frequency is set as a vertical axis. The distancemeasurement control unit 24 derives the distance to the subjectcorresponding to a maximum value of the measurement frequency in theabove-described histogram as a measurement result and outputs distancedata indicating the derived measurement result to the main control unit26. A histogram may be generated based on the reciprocation time (theelapsed time from light emission to light reception) of the laser beamor ½ of the reciprocation time of the laser beam, or the like, insteadof the distance to the subject.

The pause period refers to a period for pausing the driving of the laserdiode 32 and the photodiode 36. In the distance measurement device 10 ofthis embodiment, as a specific example, as shown in FIG. 2 , the pauseperiod is set to several 100 msec.

In the distance measurement device 10 of this embodiment, the singlemeasurement time is set to several 100 msec.

In a case of not performing imaging, the main control unit 26 of thedistance measurement device 10 of this embodiment displays a live viewimage on the view finder 46 as described above. The main control unit 26performs the display of the live view image by displaying the capturedimages captured in several 10 fps (several 10 msec/image) on the viewfinder 46 as a motion image. For this reason, during the singlemeasurement period, live view images for several 10 are displayed on theview finder 46.

Next, the imaging operation and the distance measurement operation in acase where the imaging operation and the distance measurement operationin the distance measurement device 10 of this embodiment aresynchronized will be described. Hereinafter, as a specific example, animaging operation and a distance measurement operation in a case wherean imaging operation to capture a still image and a distance measurementoperation are synchronized will be described.

First, control processing which is executed by the main control unit 26will be described. FIG. 5 is a flowchart showing an example of a flow ofcontrol processing which is executed by the main control unit 26 of thedistance measurement device 10 of this embodiment.

The flowchart shown in FIG. 5 is executed if power is supplied to thedistance measurement device 10.

First, in Step 100, the main control unit 26 starts a live viewoperation. As described above, the main control unit 26 displays thelive view image on the view finder 46 by performing control forcontinuously displaying the captured images obtained by the imagingoptical system 40 and the imaging element 42 as a motion image.

Next, in Step 102, the main control unit 26 determines whether or notthe release button of the operating unit 44 is half-pressed. In a casewhere the release button is not half-pressed, for example, in a casewhere the release button is not pressed at all, or the like, the processprogresses to Step 132. In a case where the release button ishalf-pressed, the process progresses to Step 104.

Next, in Step 104, the main control unit 26 controls the imaging opticalsystem 40 and performs AE and AF described above. In the distancemeasurement device 10, exposure adjustment is performed by performingAE, focusing control is performed by performing AF, and image lightindicating the subject is formed on the light receiving surface of theimaging element 42 in a focused state.

Next, in Step 105, the main control unit 26 transmits exposure state forspecifying an exposure state at the present time as a result of AE tothe distance measurement control unit 24. In Step 105, the main controlunit 26 also transmits focusing state specification information forspecifying a focusing state at the present time as a result of AF to thedistance measurement control unit 24. Examples of the exposure statespecification information include an F-number and a shutter speeduniquely determined according to subject brightness, or an F-number anda shutter speed derived from a so-called AE evaluation value uniquelydetermined according to subject brightness. Other examples of theexposure state specification information include an AE evaluation value.Examples of the focusing state specification information include thesubject distance obtained by AF. Hereinafter, for convenience ofdescription, in a case where there is no need for distinction betweenthe exposure state specification information and the focusing statespecification information, these are referred to as “specificationinformation”.

Next, in Step 106, the main control unit 26 determines whether or notthe release button of the operating unit 44 is fully pressed. In a casewhere the release button is not fully pressed, the process progresses toStep 108.

In Step 108, the main control unit 26 determines whether or not apressing operation to the release button of the operating unit 44 isreleased. In a case where pressing is not released, the process returnsto Step 104, and this processing is repeated. In a case where pressingis released, the process progresses to Step 132.

In a case where the release button is fully pressed, the processprogresses from Step 106 to Step 110.

In Step 110, the main control unit 26 transmits the synchronizationsignal to the distance measurement control unit 24. In this way, in thedistance measurement device 10 of this embodiment, in order tosynchronize the imaging operation by the main control unit 26 with thedistance measurement operation by the distance measurement control unit24, prior to the start of the imaging (actual exposure to the imagingelement 42), the synchronization signal is transmitted from the maincontrol unit 26 to the distance measurement control unit 24. Thoughdetails will be described below, in the distance measurement controlunit 24, if the synchronization signal is received, the distancemeasurement operation (the measurement of the distance to the subject)starts.

Next, in Step 112, the main control unit 26 starts the actual exposure(imaging). With the start of the actual exposure, the pixels of theimaging element 42 are irradiated with light (image light is formed onthe light receiving surface of the imaging element 42), and signalcharges according to irradiated light are stored in the respectivepixels.

Next, in Step 114, the main control unit 26 detects whether or not theactual exposure ends. The process is in a standby state until the actualexposure ends, and in a case where the actual exposure ends, the processprogresses to Step 116. A determination method of whether or not theactual exposure ends is not limited, and as a specific example, adetermination method based on determination of whether or not an actualexposure time determined under various conditions has elapsed is used.

In Step 116, the main control unit 26 starts the reading of the signalcharges stored in the respective pixels of the imaging element 42.

Next, in Step 118, the main control unit 26 outputs a reading startsignal indicating the start of the reading to the distance measurementcontrol unit 24. The signal charges read from the respective pixels aretransmitted to the main control unit 26 as electrical signals (imagesignals), which are digital signals according to the signal charges.

Next, in Step 120, the main control unit 26 determines whether or not itis the horizontal blanking period. As described above, in a case ofreading the signal charges from the pixels of the imaging element 42,since the signal charges are read in units of pixels for each pixel row,the horizontal blanking period during which the reading of the signalcharges are not performed is generated between the pixel rows. The maincontrol unit 26 determines whether or not it is the horizontal blankingperiod, and in a case where it is not the horizontal blanking period,for example, while the signal charges are read from the pixels of onepixel row, the process progresses to Step 124. In a case of thehorizontal blanking period, the process progresses to Step 122.

In Step 122, the main control unit 26 transmits a light emissioninstruction signal to the distance measurement control unit 24. Thoughdetails will be described below, if the light emission instructionsignal is received, the distance measurement control unit 24 causes thelaser diode 32 to emit light based on the received light emissioninstruction signal.

Next, in Step 124, the main control unit 26 determines whether or not toend the reading. In a case where the signal charges are not yet readfrom all pixels of the imaging element 42, the process returns to Step120, and this processing is repeated. In a case where the signal chargesare read from all pixels of the imaging element 42, the processprogresses to Step 126.

In Step 126, the main control unit 26 transmits a reading end signalindicating the end of the reading to the distance measurement controlunit 24.

Next, in Step 128, the main control unit 26 determines whether or notdistance data is received. Though details will be described below, ifthe distance measurement is performed, the distance measurement controlunit 24 transmits distance data indicating a measurement result (finallyderived distance) to the main control unit 26. The main control unit 26is in a standby state until distance data transmitted from the distancemeasurement control unit 24 is received, and in a case where distancedata is received, progresses to Step 130.

In Step 130, the main control unit 26 displays information relating tothe distance to the subject on the view finder 46 based on receiveddistance data so as to be superimposed on a live view image. The maincontrol unit 26 stores received distance data in the storage unit 48 incorrelation with a captured image obtained by imaging. With this step,the captured image (image data indicating the captured image) obtainedby imaging the subject and the distance (distance data) to the subjectare stored in the storage unit 48 in correlation with each other.

Next, in Step 132, the main control unit 26 determines whether or not apower switch (not shown) is turned off. In a case where the power switchis not turned off, the process returns to Step 102, and this processingis repeated. In a case where the power switch is turned off, the processprogresses to Step 134.

In Step 134, the main control unit 26 stops the live view operation, andthen, ends this processing. The main control unit 26 turns off the powersupply of the distance measurement device 10.

Next, distance measurement processing which is executed by the distancemeasurement control unit 24 will be described. FIGS. 6A and 6B areflowcharts showing an example of a flow of distance measurementprocessing which is executed by the distance measurement control unit 24of the distance measurement device 10 of this embodiment. FIG. 7 is anexample of a timing chart showing the timings of the imaging operationand the distance measurement operation.

The flowcharts shown in FIGS. 6A and 6B are executed if power issupplied to the distance measurement device 10.

First, in Step 192, the distance measurement control unit 24 determineswhether or not the specification information transmitted in Step 105 ofthe above-described control processing is received. In Step 192, in acase where the specification information is not received, thedetermination is negative, and the distance measurement control unit 24performs the determination of Step 192 again. In Step 192, in a casewhere the specification information is received, the determination isaffirmative, and the process progresses to Step 194.

Next, in Step 196, the distance measurement control unit 24 determinesan effective distance measurement range (an example of a distance rangeaccording to the technique of the present disclosure) based on thefocusing state specification information received in Step 192. Forexample, the distance measurement control unit 24 determines theeffective distance measurement range with reference to a rangederivation table (not shown) in which an effective distance measurementrange is uniquely derived from the focusing state specificationinformation.

The effective distance measurement range is a distance range which isused when determining the frequency of each distance obtained byperforming the derivation of the distance to the subject multiple times.That is, the effective distance measurement range indicates an effectiverange of a distance to be derived in Step 222 described below, and meansthe range of a subject distance estimated from the focusing statespecification information and the vicinity thereof.

Examples of the range derivation table include a table in which a movingdirection and a moving distance of a focus lens from a referenceposition determined in advance are correlated with an effective distancemeasurement range. The moving direction and the moving distance arespecified by the focusing state specification information.

The distance measurement control unit 24 may determine the effectivedistance measurement range using an arithmetic expression with thefocusing state specification information as an independent variable andthe effective distance measurement range as a dependent variable aswithout using the range derivation table.

Next, in Step 198, the distance measurement control unit 24 determines aderivation resolution uniquely determined from the effective distancemeasurement range determined in Step 196.

The derivation resolution is a resolution increased according to theeffective distance measurement range determined in Step 196 and is setto be higher than a predetermined resolution. The predeterminedresolution used herein indicates, for example, a resolution which isused in a case of performing a distance measurement (in a case ofderiving the distance to the subject) without being bound by theeffective distance measurement range. In this embodiment, as an exampleof the derivation resolution, a resolution which is set to be higherthan the predetermined resolution using a number of bits (for example, 8bits) determined in advance as the number of bits defining thepredetermined resolution is used.

Next, in Step 200, the distance measurement control unit 24 determineswhether or not the synchronization signal is received. Specifically, thedistance measurement control unit 24 determines whether or not thesynchronization signal transmitted from the main control unit 26 in Step110 of the control processing in the main control unit 26 describedabove is received. The process is in a standby state until thesynchronization signal is received, and if the synchronization signal isreceived, the process progresses to Step 202.

In Step 202, the distance measurement control unit 24 transits to thevoltage adjustment period shown in FIG. 7 as an example and performsvoltage adjustment of the drive voltage of the laser diode 32 and thephotodiode 36. With this, the emission intensity of the laser beam ofthe laser diode 32 is adjusted and the light receiving sensitivity ofthe photodiode 36 is adjusted.

The emission intensity of the laser beam emitted from the laser diode 32is adjusted based on the specification information received in Step 192.For example, the distance measurement control unit 24 adjusts theemission intensity of the laser beam with reference to an intensitysetting table (not shown) in which voltage information indicating thedrive voltage of the laser diode 32 is uniquely derived from thespecification information. That is, the distance measurement controlunit 24 derives the voltage information corresponding to thespecification information received in Step 192 from the intensitysetting table and performs the voltage adjustment such that the drivevoltage indicated by the derived voltage information is applicable tothe laser diode 32 (see FIG. 10 ).

Examples of the intensity setting table include a table in which voltageinformation representing the shorter a distance to a principal subject,the lower the emission intensity of the laser beam, and the smaller theamount of ambient light (the larger the exposure), the lower theemission intensity of the laser beam is stored. The distance to theprincipal subject is specified by the focusing state specificationinformation, and the amount of ambient light is specified by theexposure state specification information. Ambient light becomes noisefor the laser beam, and this means that the smaller the amount ofambient light (the larger the exposure), the smaller the noise of thelaser beam becomes. Accordingly, in Step 202, the distance measurementcontrol unit 24 performs the voltage adjustment such that the emissionintensity of the laser beam becomes small in a case where the amount ofambient light is small. Since the exposure becoming large means thatsubject brightness becomes low, the lower the subject brightness, thelower the emission intensity may be set.

The distance measurement control unit 24 may adjust the emissionintensity of the laser beam based on the voltage information derived byan arithmetic expression with the exposure state specificationinformation and the focusing state specification information asindependent variables and the voltage information as a dependentvariable without using the intensity setting table.

Here, although a case where the emission intensity of the laser beam isadjusted based on the exposure state specification information and thefocusing state specification information received in Step 192 has beenillustrated, the technique of the present disclosure is not limitedthereto. For example, the emission intensity of the laser beam may beadjusted based on the exposure state specification information or thefocusing state specification information.

The light receiving sensitivity of the photodiode 36 is adjusted basedon the focusing state specification information received in Step 192.For example, the distance measurement control unit 24 adjusts the lightreceiving sensitivity of the photodiode 36 with reference to asensitivity adjustment table (not shown) in which the voltageinformation indicating the drive voltage of the photodiode 36 isuniquely derived from the specification information. That is, thedistance measurement control unit 24 derives the voltage informationcorresponding to the focusing state specification information receivedin Step 192 from the sensitivity adjustment table and performs thevoltage adjustment such that the drive voltage indicated by the derivedvoltage information is applicable to the photodiode 36 (see FIG. 10 ).

Examples of the sensitivity adjustment table include a table in whichvoltage information representing the shorter the distance to theprincipal subject, the lower the light receiving sensitivity of thephotodiode 36 is stored.

The distance measurement control unit 24 may set the light receivingsensitivity of the photodiode 36 based on voltage information derived byan arithmetic expression with the focusing state specificationinformation as an independent variable and the voltage information as adependent variable without using the sensitivity adjustment table.

Next, in Step 204, the distance measurement control unit 24 determineswhether or not the voltage adjustment ends. In this embodiment, as anexample, as shown in FIG. 7 , the voltage adjustment period is set toseveral 100 msec. For this reason, the distance measurement control unit24 determines that the voltage adjustment ends in a case where several100 msec have elapsed after the transition to the voltage adjustmentperiod. Accordingly, the distance measurement control unit 24 determinesthat the voltage adjustment does not end and is in a standby state untilseveral 100 msec have elapsed after the transition to the voltageadjustment period, and in a case where several 100 msec have elapsed,determines that the voltage adjustment ends and progresses to Step 206.

In Step 206, the distance measurement control unit 24 transits to themeasurement period and starts to measure the distance to the subject.

Next, in Step 208, the distance measurement control unit 24 determineswhether or not the reading start signal is received. Specifically, thedistance measurement control unit 24 determines whether or not thereading start signal transmitted from the main control unit 26 in Step118 of the control processing in the main control unit 26 describedabove is received. In the distance measurement control unit 24 of thedistance measurement device 10 of this embodiment, since control in themeasurement of the distance to the subject is different between a period(hereinafter, referred to as a “reading period”) during which the chargesignals are read from the pixels and a period out of the reading period,the reading start signal is received from the main control unit 26.Then, control in the measurement, specifically, control for lightemission of the laser diode 32 is different according to the presence orabsence of reception of the reading start signal. In order to make thelaser diode 32 emit light, the drive voltage for driving the laser diode32 is applied to the laser diode 32. If the drive voltage is applied tothe laser diode 32 while the charge signals are being read from thepixels of the imaging element 42, in the distance measurement device 10,variation in voltage may occur, and noise may be superimposed on thecharge signals read from the pixels due to variation in voltage. In thisway, disruption may occur in the captured image due to noisesuperimposed on the charge signals.

For this reason, the distance measurement control unit 24 of thedistance measurement device 10 of this embodiment performs control suchthat, in a reading period, the laser diode 32 emits light in theabove-described horizontal blanking period which is a period duringwhich the charge signals are not read from the pixels. That is, thedistance measurement control unit 24 performs control such that, in thereading period, the laser diode 32 emits light in synchronization withthe imaging operation.

As described above, in a period out of the reading period, sincesuperimposition of noise due to variation in voltage does not cause aproblem, the laser diode 32 may not emit light in synchronization withthe imaging operation.

In this case, as described above, the laser diode 32 may emit lightevery several msec according to each measurement. Hereinafter, controlby the distance measurement control unit 24 in a period out of thereading period is referred to as “normal control”.

In Step 208, since the distance measurement control unit 24 performs thenormal control in a case where the reading start signal is not received,the process progresses to Step 216. In a case where the distancemeasurement control unit 24 receives the reading start signal, theprocess progresses to Step 210.

In Step 210, the distance measurement control unit 24 determines whetheror not the reading end signal is received. Specifically, the distancemeasurement control unit 24 determines whether or not the reading endsignal transmitted from the main control unit 26 in Step 126 of thecontrol processing in the main control unit 26 described above isreceived.

Since the distance measurement control unit 24 performs the normalcontrol in a subsequent period in a case where the reading end signal isreceived, the process progresses to Step 216. In a case where thedistance measurement control unit 24 does not receive the reading endsignal, the process progresses to Step 212.

In Step 212, the distance measurement control unit 24 determines whetheror not the light emission instruction signal is received. Specifically,the distance measurement control unit 24 determines whether or not thelight emission instruction signal transmitted from the main control unit26 in Step 122 of the control processing in the main control unit 26described above is received.

In a case where the distance measurement control unit 24 does notreceive the light emission instruction signal, that is, in a case whereit is in the reading period and it is not yet in the horizontal blankingperiod, the process is in the standby state. In a case where thedistance measurement control unit 24 receives the light emissioninstruction signal, the process progresses to Step 214.

In Step 214, it is determined whether or not the measurement is beingperformed. In the distance measurement device 10 of this embodiment, theinterval (the reading time of the charge signals from the pixels of onepixel row) between the horizontal blanking periods is shorter than thesingle measurement time (in the specific example described above,several msec). For this reason, before the measurement ends, the nexthorizontal blanking period may be reached, and the light emissioninstruction signal may be transmitted from the main control unit 26 tothe distance measurement control unit 24. The distance measurementcontrol unit 24 of this embodiment neglects the received light emissioninstruction signal in a case where the light emission instruction signalis received during the measurement, whereby the laser diode 32 does notemit light. For this reason, in a case where the measurement is beingperformed, the process progresses to Step 226. In a case where themeasurement is not being performed, the process progresses to Step 216.

In Step 216, the distance measurement control unit 24 causes the laserdiode 32 to emit light such that a laser beam having emission intensityadjusted in Step 202 is emitted.

Next, in Step 218, the distance measurement control unit 24 determineswhether or not a predetermined time has elapsed. Specifically, asdescribed above, since the single measurement time is set to severalmsec, the distance measurement control unit 24 determines whether or notseveral msec have elapsed. In a case where the predetermined time (inthis embodiment, several msec which are the single measurement time) hasnot elapsed, the process is in the standby state, and in a case wherethe predetermined time has elapsed, the process progresses to Step 220.

The laser diode 32 emits light through the processing of Step 216,whereby the laser beam is emitted toward the subject through the lightemitting lens 30. The laser beam reflected from the subject is receivedby the photodiode 36 through the light receiving lens 34 until thepredetermined time elapses. The distance measurement control unit 24acquires the elapsed time from light emission to light reception in acase where the laser beam is received by the photodiode 36 and storesthe elapsed time in the storage unit (for example, the RAM or the likein the distance measurement control unit 24).

For example, in a case where the subject moves, or the like, the elapsedtime from light emission to light reception of the laser beam exceedsseveral msec, and the laser beam may not be returned (reflected lightmay not be received). In this case, a measurement error occurs. In acase where a measurement error occurs, the distance measurement controlunit 24 stores the effect in the storage unit (for example, the RAM orthe like in the distance measurement control unit 24), and theoccurrence of the measurement error may be displayed on the view finder46 or the like according to the frequency of the occurrence of themeasurement error, for example, if the frequency is not negligible inderiving the distance to the subject using a histogram. In this way, ina case where a measurement error occurs, the main control unit 26 maynot store the captured image in the storage unit 48. In this case, theuser can set whether or not to store the captured image through theoperating unit 44 (an example of a storage setting unit according to thetechnique of the present disclosure).

Next, in Step 220, the distance measurement control unit 24 determineswhether or not a predetermined number of measurements end. In Step 220,in a case where a predetermined number of measurements end, thedetermination is affirmative, and the process progresses to Step 222. InStep 220, in a case where a predetermined number of measurements do notend, the determination is negative, and the process progresses to Step208.

In Step 222, first, the distance measurement control unit 24 derives thedistance to the subject based on the time from when the laser beam isemitted through the processing of Step 216 until the photodiode 36receives the laser beam. As an example, as shown in FIG. 4 , thedistance measurement control unit 24 generates a histogram of thederived distance to the subject with the predetermined resolution. Next,as an example, as shown in FIG. 4 , the distance measurement controlunit 24 reconstructs a histogram of the distance to the subject usingthe derivation resolution within the effective distance measurementrange determined in the processing of Step 196. The distance measurementcontrol unit 24 analyzes the histogram within the effective distancemeasurement range and generates distance data representing the analyzeddistance (in the example shown in FIG. 4 , the distance having themaximum measurement frequency). Here, the distance represented bydistance data is a final distance (final output) which is provided tothe user.

The histogram generated with the derivation resolution is segmented incontrast to the histogram generated with the predetermined resolution.Accordingly, the distance obtained by analyzing the histogram isexpressed in units of minute numerical values (units of smallernumerical values) in contrast to the distance obtained by analyzing thehistogram generated with the predetermined resolution.

Next, in Step 224, the distance measurement control unit 24 transmitsdistance data generated in Step 222 to the main control unit 26, andthen, the process progresses to Step 226.

In Step 226, the distance measurement control unit 24 determines whetheror not conditions (end conditions) determined in advance as conditionsfor ending this distance measurement processing are satisfied. Anexample of the end conditions is a condition that an end instructionfrom the user is received by the operating unit 44. In Step 226, in acase where the end conditions are not satisfied, the determination isnegative, and the process progresses to Step 212. In Step 226, in a casewhere the end conditions are satisfied, the determination isaffirmative, and this distance measurement processing ends.

As described above, in the distance measurement device 10 according tothis embodiment, control is performed such that the imaging period andthe distance measurement period overlap each other. Accordingly, thedistance measurement device 10 can efficiently execute imaging and adistance measurement compared to a case where an imaging period and adistance measurement period do not overlap each other.

In the distance measurement device 10 according to this embodiment,control is performed such that the timing at which imaging is startedand the distance measurement start timing are synchronized with eachother. Accordingly, the distance measurement device 10 can efficientlyexecute imaging and a distance measurement compared to a case where adistance measurement is started at the timing later than the timing atwhich imaging is started.

In the distance measurement device 10 according to this embodiment,control is performed such that the timing at which the actual exposureis started and the distance measurement start timing are synchronizedwith each other. Accordingly, the distance measurement device 10 canefficiently execute imaging and a distance measurement compared to acase where a distance measurement is started at the timing later thanthe timing at which actual exposure is started.

In the distance measurement device 10 according to this embodiment,information relating to the distance having a high frequency among thedistances obtained by performing the derivation of the distance to thesubject multiple times is displayed on the view finder 46. Accordingly,the distance measurement device 10 can provide information relating to adistance highly necessary for the user to the user compared to a casewhere a configuration in which information relating to the distancehaving a high frequency among the distances obtained by performing thederivation of the distance to the subject multiple times is displayed onthe view finder 46 is not provided.

In the distance measurement device 10 according to this embodiment, theeffective distance measurement range is determined based on the focusingstate specification information when the distance to the subject isderived, and the distance to the subject is derived based on thedetermined effective distance measurement range. Accordingly, thedistance measurement device 10 can derive a final distance within adistance range focused by the user compared to a case where theeffective distance measurement range is not determined based on thefocusing state specification information.

In the distance measurement device 10 according to this embodiment, thedistance to the subject is derived with the resolution increasedaccording to the effective distance measurement range determined basedon the focusing state specification information. Accordingly, thedistance measurement device 10 can minutely derive a final distancecompared to a case where the distance to the subject is derived withoutusing the resolution increased according to the effective distancemeasurement range.

In the distance measurement device 10 according to this embodiment, thelaser beam having the emission intensity adjusted according to at leastone of the focusing state specification information or the exposurestate specification information is emitted from the laser diode 32.Accordingly, the distance measurement device 10 can suppress theemission of the laser beam by the laser diode 32 in a state where theemission intensity is excessive and deficient compared to a case wherethe emission intensity of the laser beam is adjusted without using thefocusing state specification information and the exposure statespecification information.

In the distance measurement device 10 according to this embodiment,reflected light of the laser beam from the subject is received by thephotodiode 36 with the light receiving sensitivity adjusted according tothe focusing state specification information. Accordingly, the distancemeasurement device 10 can suppress the reception of reflected light bythe photodiode 36 in a state where the light receiving sensitivity isexcessive and deficient compared to a case where the light receivingsensitivity of the photodiode 36 is adjusted without using the focusingstate specification information.

In the distance measurement device 10 according to this embodiment, alive view image is displayed on the view finder 46 and informationrelating to the distance to the subject is displayed on the view finder46 in parallel with the display of the live view image. Accordingly, thedistance measurement device 10 can make the user accurately ascertainthe relationship between the state of the subject and the distance tothe subject compared to a case where information relating to thedistance to the subject is not displayed on the view finder 46 inparallel with the display of the live view image.

In the above-described embodiment, although a case where a timing atwhich the actual exposure is started and the distance measurement starttiming are synchronized with each other has been illustrated, thetechnique of the present disclosure is not limited thereto. For example,the timing at which the actual exposure ends and the distancemeasurement start timing may be synchronized with each other. In thiscase, for example, in a case where the determination in Step 114 isaffirmative, the synchronization signal may be transmitted to thedistance measurement control unit 24. With this, the distancemeasurement device 10 can efficiently execute imaging and a distancemeasurement compared to a case where a distance measurement is startedat the timing later than the timing at which actual exposure ends.

The reading end timing of the signal charges and the distancemeasurement start timing may be synchronized with each other. In thiscase, for example, when the processing of Step 126 ends, thesynchronization signal may be transmitted to the distance measurementcontrol unit 24. With this, the distance measurement device 10 canefficiently execute imaging and a distance measurement compared to acase where a distance measurement is started at the timing later thanthe reading end timing of the signal charges.

In the above-described embodiment, although a case where the voltageadjustment is performed simultaneously with the distance measurementstart timing and the actual exposure start timing has been illustrated,the technique of the present disclosure is not limited thereto, and asan example, as shown in FIG. 8 , the voltage adjustment may be performedprior to the start of the distance measurement and the start of theactual exposure.

In the above-described embodiment, although a case where the histogramof the distance to the subject in terms of the measurement frequency isgenerated has been illustrated, the technique of the present disclosureis not limited thereto. For example, a histogram of the time requiredfor the reciprocation from the emission to the reception of the laserbeam in terms of the measurement frequency may be generated.Furthermore, a time range corresponding to an effective distancemeasurement range may be set and a histogram may be reconstructed with aresolution increased according to the time range. In this case, forexample, the distance to the subject derived based on the time of amaximum value of the reconstructed histogram may be set as the distanceto be finally output (the distance to be presented to the user).

In the above-described embodiment, as an example, as shown in FIGS. 4and 9A, although a case where both end portions of the histogram for alldata are not included in the effective distance measurement range (inthe example shown in FIG. 9A, a non-hatched range) has been illustrated,the technique of the present disclosure is not limited thereto, and asan example, as shown in FIGS. 9B and 9C, one end portion (hatchedportion) of the histogram may not be included in the effective distancemeasurement range (in the examples shown in FIGS. 9B and 9C, anon-hatched range).

In the above-described embodiment, for convenience of description,although a case where the histogram (histogram for all data) which isgenerated once is reconstructed based on the effective distancemeasurement range has been illustrated, the technique of the presentdisclosure is not limited thereto. For example, the distance measurementcontrol unit 24 may generate a histogram for the distances excluding thedistances outside the effective distance measurement range among thedistances (all data) to the subject obtained by performing thederivation multiple times. In this case, the distance measurementcontrol unit 24 may generate the histogram with the above-describedderivation resolution.

In the above-described embodiment, although a case where informationrelating to the distance to the subject is displayed on the view finder46 so as to be superimposed on a live view image has been illustrated,the technique of the present disclosure is not limited thereto. Forexample, information relating to the distance to the subject may bedisplayed in a display area different from the display area of the liveview image. In this way, information relating to the distance to thesubject may be displayed on the view finder 46 in parallel with thedisplay of the live view image.

In the above-described embodiment, although a case where the releasebutton provided in the distance measurement device 10 is operated hasbeen illustrated, the technique of the present disclosure is not limitedthereto. For example, AE and AF may be started in response to an imagingpreparation instruction received by a user interface (UI) unit of anexternal device used in the form of being connected to the distancemeasurement device 10, and actual exposure may be started in response toan imaging instructed received by the UI unit of the external device.Examples of the external device used in the form of being connected tothe distance measurement device 10 include a smart device, a personalcomputer (PC), or a spectacles type or a wristwatch type wearableterminal device.

In the above-described embodiment, although a case where the live viewimage and the distance measurement result (information relating to thedistance to the subject) are displayed on the view finder 46 has beenillustrated, the technique of the present disclosure is not limitedthereto. For example, at least one of the live view image or thedistance measurement result may be displayed on a display unit of theexternal device used in the form of being connected to the distancemeasurement device 10. Examples of the display unit of the externaldevice used in the form of being connected to the distance measurementdevice 10 include a display of a smart device, a display of a PC, or adisplay of a wearable terminal device.

In the above-described embodiment, for convenience of description,although description has been provided on an assumption that there is noAF error, the technique of the present disclosure is not limitedthereto. That is, the distance measurement control unit 24 may derivethe distance as described above in a case where an AF error does notoccur, and may not derive the distance in a case where an AF erroroccurs.

In the above-described embodiment, for convenience of description,although description has been provided on an assumption that there is noAE error, the technique of the present disclosure is not limitedthereto. That is, the distance measurement control unit 24 may derivethe distance as described above in a case where an AE error does notoccur, and may not derive the distance in a case where an AE erroroccurs.

In the above-described embodiment, although the focus adjustment and theexposure adjustment by AF and AE have been illustrated, the technique ofthe present disclosure is not limited thereto, focus adjustment bymanual focus and exposure adjustment by manual exposure may be applied.

In the above-described embodiment, although a case where the techniqueof the present disclosure is applied to the distance measurement device10 has been illustrated, the technique of the present disclosure is notlimited thereto, and the technique of the present disclosure may beapplied to a digital camera (imaging device).

In the above-described embodiment, although a case where the voltageadjustment is performed in Step 202 has been illustrated, the techniqueof the present disclosure is not limited thereto, and the voltageadjustment may not necessarily be performed.

The control processing (see FIG. 5 ) and the distance measurementprocessing (see FIGS. 6A and 6B) described in the above-describedembodiment are merely examples. Accordingly, it is needless to say thatunnecessary steps may be deleted, new steps may be added, or theprocessing order may be rearranged without departing the gist of theinvention. The respective processing included in the control processingand the distance measurement processing described in the above-describedembodiment may be realized by a software configuration using a computerby executing a program, or may be realized by other hardwareconfigurations. Furthermore, the respective processing may be realizedby a combination of a hardware configuration and a softwareconfiguration.

In the above-described embodiment, although a case where the lightemission frequency of the laser beam is fixed has been illustrated, thetechnique of the present disclosure is not limited thereto. Sinceambient light becomes noise for the laser beam, the light emissionfrequency of the laser beam may be a light emission frequency determinedaccording to subject brightness.

Hereinafter, an example of a way of determining the light emissionfrequency of the laser beam will be described.

The light emission frequency of the laser beam is derived from a lightemission frequency determination table 300 shown in FIG. 11 as anexample. In the light emission frequency determination table 300, thesubject brightness and the light emission frequency of the laser beamare correlated with each other such that the higher the subjectbrightness, the larger the light emission frequency of the laser beambecomes. That is, in the light emission frequency determination table300, the subject brightness has a magnitude relationship of L₁<L₂< . . .<L_(n), and the light emission frequency has a magnitude relationship ofN₁<N₂< . . . <N_(n). In the example shown in FIG. 2 , although the lightemission frequency in units of 100 times has been illustrated, theinvention is not limited thereto, and the light emission frequency maybe determined in units often times or once by the light emissionfrequency determination table 300.

In the distance measurement device 10, in order to realize thederivation of the light emission frequency of the laser beam by thelight emission frequency determination table 300, brightness informationtransmission processing (see FIG. 12 ) is executed by the main controlunit 26, and light emission frequency determination processing (see FIG.13 ) is executed by the distance measurement control unit 24.

First, the brightness information transmission processing which isexecuted by the main control unit 26 if the power switch of the distancemeasurement device 10 is turned on will be described referring to FIG.12 .

In the brightness information transmission processing shown in FIG. 12 ,first, in Step 400, the main control unit 26 determines whether or notbrightness acquisition start conditions which are conditions forstarting acquisition of subject brightness are satisfied. An example ofthe brightness acquisition start conditions is a condition that therelease button is half-pressed. Another example of the brightnessacquisition start conditions is a condition that the captured image isoutput from the imaging element 42.

In Step 400, in a case where the brightness acquisition start conditionsare satisfied, the determination is affirmative, and the processprogresses to Step 402. In Step 400, in a case where the brightnessacquisition start conditions are not satisfied, the determination isnegative, and the process progresses to Step 406.

In Step 402, the main control unit 26 acquires the subject brightnessfrom the captured image, and then, the process progresses to Step 404.Here, although a case where the subject brightness is acquired from thecaptured image has been illustrated, the technique of the presentdisclosure is not limited thereto. For example, if a brightness sensorwhich detects subject brightness is mounted in the distance measurementdevice 10, the main control unit 26 may acquire the subject brightnessfrom the brightness sensor.

In Step 404, the main control unit 26 transmits brightness informationindicating the subject brightness acquired in Step 402 to the distancemeasurement control unit 24, and then, the process progresses to Step406.

In Step 406, the main control unit 26 determines whether or not endconditions which are conditions for ending this brightness informationtransmission processing are satisfied. An example of the end conditionsis a condition that the power switch of the distance measurement device10 is turned off. In Step 406, in a case where the end conditions arenot satisfied, the determination is negative, and the process progressesto Step 400. In Step 406, in a case where the end conditions aresatisfied, the determination is affirmative, and this brightnessinformation transmission processing ends.

Next, the light emission frequency determination processing which isexecuted by the distance measurement control unit 24 if the power switchof the distance measurement device 10 is turned on will be describedreferring to FIG. 13 .

In the light emission frequency determination processing shown in FIG.13 , first, in Step 410, the distance measurement control unit 24determines whether or not the brightness information transmitted byexecuting the processing of Step 404 is received. In Step 410, in a casewhere the brightness information transmitted by executing the processingof Step 404 is not received, the determination is negative, and theprocess progresses to Step 416. In Step 410, in a case where thebrightness information transmitted by executing the processing of Step404 is received, the determination is affirmative, and the processprogresses to Step 412.

In Step 412, the distance measurement control unit 24 derives the lightemission frequency corresponding to the subject brightness indicated bythe brightness information received in Step 410 from the light emissionfrequency determination table 300, and then, the process progresses toStep 414.

In Step 414, the distance measurement control unit 24 stores the lightemission frequency derived in the processing of Step 412 in the storageunit 48, and then, the process progresses to Step 416. The lightemission frequency stored in the storage unit 48 by the processing ofStep 416 means “a predetermined number of times” in Step 218 of thedistance measurement processing shown in FIG. 6B.

In Step 416, the main control unit 26 determines whether or not endconditions which are conditions for ending this light emission frequencydetermination processing are satisfied. An example of the end conditionsis a condition that the power switch of the distance measurement device10 is turned off. In Step 416, in a case where the end conditions arenot satisfied, the determination is negative, and the process progressesto Step 410. In Step 416, in a case where the end conditions aresatisfied, the determination is affirmative, and this light emissionfrequency determination processing ends.

Next, another example of a way of determining the light emissionfrequency of the laser beam will be described.

As an example, the light emission frequency of the laser beam is derivedaccording to a light emission frequency determination table 500 shown inFIG. 14 . In the light emission frequency determination table 500,exposure state specification information (E₁, E₂, . . . , E_(n))uniquely determined according to the subject brightness and the lightemission frequency (N₁, N₂, . . . , N_(n)) of the laser beam arecorrelated with each other. Here, the exposure state specificationinformation uniquely determined according to the subject brightnessmeans, for example, exposure state specification information indicatingthat, the higher the subject brightness, the lower the exposure becomes.

In a case of deriving the light emission frequency of the laser beamusing the light emission frequency determination table 500, exposurestate specification information transmission processing (see FIG. 15 )is executed by the main control unit 26, and light emission frequencydetermination processing (see FIG. 16 ) is executed by the distancemeasurement control unit 24.

First, the exposure state specification information transmissionprocessing which is executed by the main control unit 26 if the powerswitch of the distance measurement device 10 is turned on will bedescribed referring to FIG. 15 .

In the exposure state specification information transmission processingshown in FIG. 15 , first, in Step 600, the main control unit 26determines whether or not the release button is half-pressed. In Step600, in a case where the release button is not half-pressed, thedetermination is negative, and the process progresses to Step 606. InStep 600, in a case where the release button is half-pressed, thedetermination is affirmative, and the process progresses to Step 602. InFIG. 15 , although a case where the operating unit 44 comprises therelease button has been described as an example, the technique of thepresent disclosure is not limited thereto. For example, in a case wherethe operating unit 44 comprises a distance measurement imaging startbutton, Step 600 may be omitted, and in a case where power is supplied,the processing of Step 602 may be started.

In Step 602, the main control unit 26 performs AE based on the subjectbrightness acquired from the captured image, and then, the processprogresses to Step 604.

In Step 604, the main control unit 26 transmits the exposure statespecification information to the distance measurement control unit 24,and then, the process progresses to Step 606.

In Step 606, the main control unit 26 determines whether or not endconditions which are conditions for ending this exposure statespecification information transmission processing are satisfied. Anexample of the end conditions is a condition that the power switch ofthe distance measurement device 10 is turned off. In Step 606, in a casewhere the end conditions are not satisfied, the determination isnegative, and the process progresses to Step 600. In Step 606, in a casewhere the end conditions are satisfied, the determination isaffirmative, and this exposure state specification informationtransmission processing ends.

Next, the light emission frequency determination processing which isexecuted by the distance measurement control unit 24 if the power switchof the distance measurement device 10 is turned on will be describedreferring to FIG. 16 .

In the light emission frequency determination processing shown in FIG.16 , first, in Step 610, the distance measurement control unit 24determines whether or not the exposure state specification informationtransmitted by executing the processing of Step 604 is received. In Step610, in a case where the exposure state specification informationtransmitted by executing the processing of Step 604 is not received, thedetermination is negative, and the process progresses to Step 616. InStep 610, in a case where the exposure state specification informationtransmitted by the executing the processing of Step 604 is received, thedetermination is affirmative, and the process progresses to Step 612.

In Step 612, the distance measurement control unit 24 derives the lightemission frequency corresponding to the exposure state specificationinformation received in Step 610 from the light emission frequencydetermination table 500, and then, the process progresses to Step 614.

In Step 614, the distance measurement control unit 24 stores the lightemission frequency derived in the processing of Step 612 in the storageunit 48, and then, the process progresses to Step 616. The lightemission frequency stored in the storage unit 48 by the processing ofStep 616 means “a predetermined number of times” in Step 218 of thedistance measurement processing shown in FIG. 6B.

In Step 616, the main control unit 26 determines whether or not endconditions which are conditions for ending this exposure statespecification information transmission processing are satisfied. Anexample of the end conditions is a condition that the power switch ofthe distance measurement device 10 is turned off. In Step 616, in a casewhere the end conditions are not satisfied, the determination isnegative, and the process progresses to Step 610. In Step 616, in a casewhere the end conditions are satisfied, the determination isaffirmative, and this exposure state specification informationtransmission processing ends.

In this way, since the distance measurement device 10 makes the lightemission frequency (distance measurement frequency) of the laser beamlarger when the subject brightness is higher, it is possible to obtain adistance measurement result, in which the influence of noise of ambientlight is moderated, compared to a case where the light emissionfrequency (distance measurement frequency) of the laser beam is fixedregardless of the subject brightness.

In the above-described embodiment, although the laser beam has beenillustrated as light for distance measurement, the technique of thepresent disclosure is not limited thereto, and directional light whichis light having directivity may be used. For example, directional lightwhich is obtained by a light emitting diode (LED) or a super luminescentdiode (SLD) may be used. The directivity of directional light ispreferably the same directivity as the directivity of the laser beam,and is preferably, for example, the directivity usable in a distancemeasurement within a range of several meters to several kilometers.

The disclosures of Japanese Patent Application No. 2014-095557 filed onMay 2, 2014 and Japanese Patent Application No. 2014-159803 filed onAug. 5, 2014 are incorporated by reference in this specification.

All documents, patent applications, and technical specificationsdescribed in this specification are incorporated by reference in thisspecification as if each of the documents, the patent applications, andthe technical specification is concretely and respectively specified asbeing incorporated by reference herein.

In regard to the above embodiment, the following appendixes are furtherdisclosed.

Appendix 1

A distance measurement device includes an imaging unit which captures asubject image formed by an imaging optical system forming the subjectimage indicating a subject, an emission unit which emits a laser beamalong an optical axis direction of the imaging optical system, a lightreceiving unit which receives reflected light of the laser beam from thesubject, a derivation unit which derives a distance to the subject basedon a timing at which the laser beam is emitted by the emission unit anda timing at which the reflected light is received by the light receivingunit, and a control unit which performs control such that at least apart of an imaging period by the imaging unit overlaps at least a partof a distance measurement period by the emission unit, the lightreceiving unit, and the derivation unit.

Appendix 2

A distance measurement method including deriving a distance to a subjectbased on the timing at which directional light is emitted by an emissionunit emitting directional light as light having directivity along anoptical axis direction of an imaging optical system forming a subjectimage indicating the subject and a timing at which reflected light isreceived by a light receiving unit receiving the reflected light of thedirectional light from the subject, and performing control such that atleast a part of an imaging period by an imaging unit capturing a subjectimage formed by the imaging optical system overlaps at least a part of adistance measurement period.

Appendix 3

A distance measurement program which causes a computer to executeprocessing including deriving a distance to a subject based on a timingat which directional light is emitted by an emission unit emittingdirectional light as light having directivity along an optical axisdirection of an imaging optical system forming a subject imageindicating the subject and a timing at which reflected light is receivedby a light receiving unit receiving the reflected light of thedirectional light from the subject, and performing control such that atleast a part of an imaging period by an imaging unit capturing a subjectimage formed by the imaging optical system overlaps at least a part of adistance measurement period.

What is claimed is:
 1. A distance measurement method for a digitalcamera comprising: capturing, by an imaging sensor a subject image of asubject by performing actual exposure; forming, by an imaging opticalsystem, the subject image; emitting, by a light emitter, light;receiving, by a light receiver, reflected light of the light from thesubject; performing a distance measurement operation by the lightemitter and the light receiver and an imaging operation by the imagesensor; performing the distance measurement operation in which thederivation of a distance to the subject is performed multiple times soas to derive a final distance; and in a case in which an erroneousmeasurement, in which an elapsed time from a light emission to a lightreception of the light exceeds a predetermined time, or the light is notreturned to be received by the light receiver, occurs predeterminedtimes, indicating an error on a display.
 2. The distance measurementmethod according to claim 1, wherein, in a case of deriving the finaldistance, a distance range for use or a time range from the emission ofthe light to the reception of the light is determined based on focusingstate specification information of the digital camera and the finaldistance is derived within the determined distance range or thedetermined time range.
 3. The distance measurement method according toclaim 2, wherein, in a case of deriving the distance, the final distanceis derived with a resolution determined according to a result ofdetermination of the distance range or the time range.
 4. The distancemeasurement method according to claim 1, wherein emission intensity ofthe light emitter is adjusted based on at least one of focusing statespecification information of the digital camera or subject brightness orexposure state specification information of the digital camera to emitthe light.
 5. The distance measurement method according to claim 4,wherein the emission intensity is made lower when a focal distanceindicated by the focusing state specification information of the digitalcamera is shorter.
 6. The distance measurement method according to claim4, wherein the emission intensity is made lower when the subjectbrightness is lower and the emission intensity is made lower when theexposure indicated by the exposure state specification information ofthe digital camera is higher.
 7. The distance measurement methodaccording to claim 1, wherein light receiving sensitivity of the lightreceiver is adjusted based on focusing state specification informationof the digital camera to receive the reflected light.
 8. The distancemeasurement method according to claim 7, wherein the light receivingsensitivity is made lower when a focal distance indicated by thefocusing state specification information of the digital camera isshorter.
 9. The distance measurement method according to claim 1,wherein a distance measurement by the light emitter and the lightreceiver, is performed a number of times determined in advance accordingto subject brightness or exposure state specification information of thedigital camera.
 10. The distance measurement method according to claim9, wherein the distance measurement by the light emitter, and the lightreceiver is performed a larger number of times when the subjectbrightness is higher or when the exposure indicated by the exposurestate specification information of the digital camera is lower.
 11. Thedistance measurement method according to claim 1, further comprising:storing the distance, wherein the storing is stopped in a case where thederivation of the distance is impossible.
 12. The distance measurementmethod according to claim 11, further comprising: setting whether or notto stop the storing in a case where the derivation of the distance isimpossible.
 13. The distance measurement method according to claim 1,further comprising receiving a first press action for adjusting a focusdistance and a second press action for imaging the subject by the imagesensor and the second press action is an action which an image capturebutton is pressed.
 14. The distance measurement method according toclaim 1, wherein drive of the light emitter or the light receiver isadjusted according to information of an exposure state of an imagingcondition.
 15. The distance measurement method according to claim 1,wherein the light emitted by the light emitter is a directional light.16. The distance measurement method according to claim 1, wherein driveof the light emitter or the light receiver is adjusted according to adistance from the digital camera to the subject.
 17. The distancemeasurement method according to claim 15, wherein the directional lightis a laser.
 18. The distance measurement method according to claim 1,wherein a distance having a maximum measurement frequency among thedistances obtained is derived by obtaining the distance multiple timesand is derived as the final distance.
 19. The distance measurementmethod according to claim 1, wherein the distance measurement operationand the imaging operation is synchronized and wherein the light isemitted by the light emitter in a horizontal blanking period of theimaging operation.
 20. The distance measurement method according toclaim 1, wherein the final distance is derived based on the obtainedmultiple distances which are within a predetermined range.
 21. Thedistance measurement method according to claim 20, wherein thepredetermined range is based on focusing information of the imageoptical system.
 22. The distance measurement method according to claim1, wherein the final distance is derived based on focusing informationof the image optical system.
 23. The distance measurement methodaccording to claim 1, further comprising: performing control such that adisplay displays a motion image captured by the imaging sensor anddisplays information relating to the distance to the subject derived.24. The distance measurement method according to claim 1, wherein thedistance is not derived in a case where there is auto focus adjustmenterror of the imaging optical system with respect to the subject or thereis auto exposure adjustment error in a case where the imaging sensorperforms imaging.
 25. The distance measurement method according to claim23, wherein the distance is not derived in a case where there is autofocus adjustment error of the imaging optical system with respect to thesubject or there is auto exposure adjustment error in a case where theimaging sensor performs imaging.
 26. The distance measurement methodaccording to claim 1, further comprising: performing control such thatthe display superimposes information relating to the distance to thesubject for making a user accurately ascertain a relationship between astate of the subject and the final distance.
 27. The distancemeasurement method according to claim 23, further comprising: storingthe final distance in a storage in correlation with a captured image bythe image sensor.
 28. A distance measurement method for a digital cameracomprising: capturing, by an imaging sensor, a subject image of asubject by performing actual exposure; forming, by an imaging opticalsystem, the subject image; emitting, by a light emitter, a light alongan optical axis direction of the imaging optical system; receiving, by alight receiver, reflected light of the light from the subject;performing a distance measurement operation by the light emitter and thelight receiver and an imaging operation by the image sensor; andperforming the distance measurement operation in which the derivation ofa distance to the subject is performed multiple times so as to derive afinal distance, wherein the distance is not derived in a case wherethere is auto focus adjustment error of the imaging optical system withrespect to the subject or there is auto exposure adjustment error in acase where the imaging sensor performs imaging.